You won't need anything else, it is an easy mod that your 84 will benefit from though nothing you will notice. I did this to my 82 as I was modifying it. I'm sorry I can't give you specifics but the wiring is "almost" identical. There is a crossfire website out there that details this and other modifications to this engine, I used it with great luck. Maybe someone can post address, I haven't been there in almost 2 years and I've forgotten the site address. Sorry.
I just did mine and I noticed a LOT more difference. Particularly because my 84 pump was dogging out on WOT. It is a simple install. The only thing is you have to have a soldering iron. You will be soldering the ground wire where the old one was. Just heat up the old contact and pull the old wire off and stick the freshly trimmed/stripped one in its place. You might have to solder the hot wire as well but it is just as easy as the ground. (I cant believe I dont remember!). Another thing, dont worry about bare wire. Just make sure the hot wire does not have even a remote possibility to ground out.